Policy interventions and competing management paradigms shape the long-term distribution of forest harvesting across the landscape.

Industrial economic models of natural resource management often incentivize the sequential harvesting of resources based on profitability, disproportionately targeting the higher-value elements of the environment. In fisheries, this issue is framed as a problem of "fishing down the food chain" when these elements represent different trophic levels or sequential depletion more generally. Harvesting that focuses on high grading the most profitable, productive, and accessible components of environmental gradients is also thought to occur in the forestry sector. Such a paradigm is inconsistent with a stewardship ethic, entrenched in the forestry literature, that seeks to maintain or enhance forest condition over time. We ask 1) how these conflicting paradigms have influenced patterns of forest harvesting over time and 2) whether more recent conservation-oriented policies influenced these historical harvesting patterns. We use detailed harvest data over a 47-y period and aggregated time series data that span over a century on the central coast of British Columbia, Canada to assess temporal changes in how logging is distributed among various classes of site productivity and terrain accessibility, corresponding to timber value. Most of this record shows a distinct trend of harvesting shifting over time to less productive stands, with some evidence of harvesting occurring in increasingly less accessible forests. However, stewardship-oriented policy changes enacted in the mid-1990s appear to have strongly affected these trends. This illustrates both a profit-maximizing tendency to log down the value chain when choices are unconstrained and the potential of policy choices to impose a greater stewardship ethic on harvesting behavior.

[Access to the intracrevicular space in preparations for fixed prosthesis]. / Acces aux limites intra-créviculaires des préparations en prothèse fixée.

Although we know that the most favourable situation for preparations margins is above gingiva, it has been proven that in numerous clinical cases, this situation is modified in an apical direction and becomes subgingival. This location of the margins then becomes unfavourable from a periodontal point of view as well as in the control of adaptation. However, the major problem arises when the impression is taken. In fact, the marginal gingiva constitutes an obstacle to the access of the impression material to these margins. Nevertheless, numerous techniques allow the free marginal gingiva to be retracted under such conditions that the principal aim can be reached without injuring the conjunctive epithelio-connection. The procedures used to retract the gingiva are either mechanical, chemico-mechanical or surgical. The mechanical techniques may use copper bands and ring collars, the latter being the procedure of choice when indicated. Another technique uses retraction cords, providing a gingival sulcus enlargement without using impregnated cords with haemostatic or astringent solutions. This last technique, nonetheless, must be avoided if there is a risk that might lead to bleeding when the cord is removed. The second retraction technique uses these same cords impregnated with haemostatic or astringent solutions. It seems that 15.5% ferric sulfate impregnated braided cords represent the procedure of choice, allowing both the retraction of the sulcus and the total absence of bleeding, since haemostasis is ensured definitively via the situ application of the pure product. The final technique is the gingival surgery. It may use Ingraham's diamonds that simultaneously finish the subgingival preparation margins and make a superficial epithelium curettage. Following this surgical retraction, haemostasis is ensured, but the rotative instrument used provides, at once, the best profile of the internal wall of the free marginal gingiva for the impression. The second procedure is electro-surgery which provides constant results when use, thereof, is well indicated. Finally, the CO2 laser can also provide another possibility for surgical retraction. Nonetheless, it seems that the CO2 laser is not the best procedure, given the difficulties in directing it. Depending on the case, all these techniques allow the expected results to be obtained, but, unfortunately, their innocuity is not absolute. In fact, it is proven that following any type of gingival retraction, a lesion is caused both by the practitioner and the equipment used, which thus, leads to a loss of about 1/10th millimeter in the height of the free marginal gingiva.